High intensity discharge lamps are typically used when high levels of light are required over large areas and when energy efficiency and/or long life are desired. These areas include gymnasiums, large public areas, warehouses, manufacturing facilities, outdoor activity areas, roadways, parking lots, and pathways. Like fluorescent lamps, HID lamps require a ballast which provides the necessary circuit conditions for starting and maintaining their operation. When HID lamps are initially turned on, it takes anywhere from five to fifteen minutes, depending upon the particular HID lamp, for the normal light intensity level to be reached. When a momentary interruption of the line voltage occurs, the same time period is required to restore the HID lamp to its normal intensity level. For situations where the lack of light for this time period is unacceptable, standby lamps (also referred to as auxiliary lamps) are typically incorporated into the lighting system. Usually, the conventional ballasts for the HID lamps have provided a voltage supply and trigger circuitry to turn on the auxiliary lamps until the HID lamps reach their normal intensity level. Then, the auxiliary lamps are turned off by the circuitry.
Conventional ballasts can operate over wide standard input voltages, typically 208–277 volts AC, which can normally be preset by the end user. The auxiliary lamps used in conjunction with HID lamps typically only operate at 120 volts AC. Conventional ballasts typically provide a transformer for the auxiliary lamp. Trigger circuitry for the auxiliary lamp is actuated by an electromechanical relay where the coil is connected in series to the HID lamp and the relay contacts are connected in series to the auxiliary lamp. When the HID lamp breaks down, such as occurs with a temporary loss of line voltage, the full voltage is presented on the coil, the relay contacts close, and the auxiliary lamp turns on.
Conventional ballasts are being rapidly being replaced with electronic ballasts which do not provide a voltage supply and trigger circuitry for systems that require auxiliary lamps. There is thus a need in the art to supply such a system.